1. Field of the Invention
The invention relates to silane-containing polymers, to processes for preparing silane-containing polymers in the presence of silane-containing molecular weight regulators, and to their use.
2. Description of the Related Art
The prior art has disclosed a number of processes for preparing silane-containing polymers. Their preparation can take place, for example, by means of polymer-analogous reaction of functional polymers with silylating agents. U.S. Pat. No. 5,036,137, for example, describes the preparation of silylated polyvinyl alcohol, polyvinyl alcohol being reacted with 3-glycidyloxypropyltrimethoxysilane or vinyltrimethoxy silane. EP-A 581576 discloses reacting OH-functional polymers such as polyvinyl alcohol with alkyl orthosilicates or alkyl-trialkoxysilanes.
Silane-containing polymers can also be prepared by copolymerization of silane-functional ethylenically unsaturated monomers. GB-A 1407827 describes the preparation of vinyl-silanol copolymer dispersions by copolymerizing vinyltrialkoxysilanes with ethylenically unsaturated comonomers. EP-A 123927 relates to silyl-modified polyvinyl alcohols obtainable by methods which include copolymerizing vinyl esters with silyl-functional comonomers, followed by hydrolysis.
Another route is the introduction of silane groups into the polymer by terminating the polymer chain with thio compounds containing Si groups, examples being mercaptosilanes, as is described in U.S. Pat. No. 6,346,570 and in DE-A 4105601; or by terminating by means of Michael addition of functional silanes, as known from U.S. Pat. No. 6,221,994. WO-A 01/09249 discloses preparing silane-functional copolymers by copolymerization with vinyl-silane and termination of the polymer chain with mercaptosilane. Disadvantages associated with the termination of polymer chains with mercaptosilanes are their toxicity and their tendency to undergo addition to double bonds. These mercaptosilanes also have too great a tendency to regulate the molecular weight, leading to excessively sharp reduction of the molecular weight. Moreover, the reaction rate is frequently retarded. Other disadvantages associated with the use of mercaptosilanes include their tendency toward yellowing and their unpleasant odor.